Two-way signal repeater



pril 2, 1952 H. GARDEFQE 2,59 ,001

TWO-WAY SIGNAL REPEATER Filed June 4, 1948 2 SHEETS SHEET l Z0 Z M 1 l oe". I 5% IE t9 mm W e2 J1; Vc v9 *1 I1 3 INVE/VT'OK HENRI GRRDERE 17Trap/v5 ya" April 1952 H. GARDERE 2,594,007

TWO-WAY SIGNAL REPEATER Filed June 4, 1948 2 SHEETS-SHEET 2 rpa ET [3-7.2 Va +ve vg y @mwmfi Patented Apr. 22, 1952 TWO-WAY SIGNAL REPEATERHenri Garder, Paris, France, assignor to Compagnie Industrielle desTelephones, Paris, France, a corporation of France Application June 4,1948, Serial No. 31,084 In France June 26, 1947 11 Claims. 1

The present invention has for its object a device for the retransmissionof low frequency currents utilised for signalling over telephone lineswith two wires.

Such devices, commonly called low frequency signalling sets are mostoften formed, in a manner already known, by two symmetrical groups ofelectro-mechanical relays, respectively ensuring the relaying of thesignalling in the two directions of transmission.

When a low frequency signal arrives travelling in one direction on oneof the lines, it starts the first relay of the corresponding group; thelast relay of that group then branches on to the other line a lowfrequency generator, usually of the same frequency as the incidentsignal. Moreover, one of the relays of the operating group blocks therelays of the other group in order to avoid a return of signalling orsetting up oscillations,

Signalling sets are also known in which the first relay of the groupsabove mentioned is replaced by a triode vacuum tube, or by a triodegas-filled tube with a heated cathode, known as a thyratron.

However, in all these known devices, a certain number ofelectromechanical relays are still necessary.

The signalling set which is the object of the present invention utilisesgas-filled tubes with a control grid, avoiding any mechanical part, inorder to ensure the transmission of the signals in both directions, on aline of two wires, Without setting up oscillation or a return of thesignal.

All the operations which, in the known devices,

are ensured by a group or relays assigned to one direction ofretransmission, are in the present invention thus fulfilled by a singlegasfilled tube, comprising three or more electrodes. Thecompletesignalling set, therefore, only comprises, as essential parts, twotubes, plus, in certain cases, a third auxiliary tube, and excludes anypart which is not purely electronic.

The present invention is distinguished by the fact that it requires, foreach transmission direction, a thyratron of which the grid circuitcomprises a source of negative polarisation and a resistance fed by theincident signal current recti- .fied so that, when a signal arrives, ahigher voltage is developed at the terminals of this resistance and inan inverse direction to the negative tension of polarisation, theplate-circuit of the thyraton comprising a source of alternating voltageof a low frequency equal to that of the signal current it is desired totransmit, and a transformer the secondary of which feeds the portion ofline which 55 2 is downstream from the device, this device comprising,moreover, means for blocking the other thyratron which does not transmitthe signal.

Figure 1 represents a first example. 0 and e designate the extremitiesof the signalling system. They are connected respectively at Ol, 02, andel, c2 to the extremities of the two lines forming part of the two wirecircuit (in parallel or in series with the extremities of the repeater,not represented, connecting the two lines) fe, ,fo are the filtersallowing only the signalling frequency to pass; tgo, tpo, tbo, tge, tpc,the, are transformers operating for the signalling frequency; rgo, rge,rbo, rbe, are rectifiers. lo and le are gas-filled triodes with cold orheated cathode; the anode of the triodes lo and le is fed by analternating source Sfb of low frequency, the frequency equal to that ofthe signalling (this source is represented in duplicate for simplicityin the diagram).

The grids are polarised negatively by a source cg, so that in theabsence of a signal none of the tubes can be lit by the voltage from thesource of the anode Sfb. The operation is as follows:

Let us suppose that a signal consisting of a train of alternating wavesof the signalling frequency presents itself at 0. It passes into thefilter ,fo, into the transformer too, is rectified in the rectifierassembly 1'90, and gives into the grid circuit of the lamp lo, at theresistance terminals H, a continuous constant positive voltage, thealternating components of the rectification being short-circuited by thecondenser Cl. Under the effect of this positive polarisation voltagethus applied to the grid, which voltage cuts itself 01? from the cgbattery voltage, the tubelo lights up durin each positive half-cyclefrom the source Sfb. The periodic current thus produced delivers intothe transformer winding cc of the trans former tpo, an amplifiedalternating current which, after having passed through the filter fesuppressing its harmonics, is emitted at the extremity c, thus ensuringthe retransmission of the signal.

Reduced to the portion described above and completed by symmetry for theother direction of transmission, the device would not operate correctly.Indeed, the current retransmitted on the side'e would cause a positivepolarisation ofthe grid of lo by the intermediary of tgc and rye,lighting up the tube le in the same manner as Z0, resulting in return ofsignalling or the setting up of oscillations.

To remedy this, there is provided, as in known signalling sets withelectro-mechanical relays, a

blocking of the retransmission system which has to remain idle.

This blocking operates in the following manner: the winding be of thetransformer tbo, previously xplained, is the source of an alternatingvoltage which, through the rectifier rbe, delivers across the terminalsof the resistance M a negative direct voltage smoothed out by C4,continuous negative. This negative voltage blocks the tube 26, that is,it prevents it from lighting up. In other words, the transformers tpo,tho and toe are provided in order that the positive voltage in the gridcircuit of 16, at the terminals of 72, due to the signal retransmittedtowards e, may be lower than the negative voltage introduced into thesame grid circuit by the blocking device (he, The, 04) at the terminalsof the resistance 14.

This device is completed by symmetry, as indicated in Figure l, forretransmission in the direction eO.

The system described allows therefore of the retransmission of thesignalling in both directions without any mechanical part.

Figure 2 represents the plan of another example, of a signalling setaccording to the present invention. In this example, one utilises athird gas-filled tube la, but whereas, in the preceding example, it wasnecessary to utilise an anode source Sfb alternating in the frequency ofthe signals, here one utilises a continuous anode source m which may bethe common anode source of the repeaters of a station.

The parts having the same markings as in the preceding example have the'same functions. The other parts cooperate in the alternateextinguishing and lighting, at the signal frequency, of the tube whichensures the retransmission. Moreover, the filters f and fe areeliminated and replaced by the filtering effect obtained by the tuningin resonance of the primaries of the transformers tub and toe, with thecondensers C5 and C6.

The rectifiers rye and me are eliminated from the secondaries of too andwe, so that it is no longer a continuous voltage which the receivedsignals produce on the grids of lo and Ze, but the alternating voltageitself of the signal, more or less amplified according to thetransformation ratio. Moreover, the transformers too and toe eachcomprise a tertiary winding 00 and ac, which are introduced in series,in the grid, circuit of the auxiliary tube, la, with a resistance r!.The grid polarisation of this lamp is ensured by a voltage 11g, as-for'the tubes lo and le.

Resistances T5, T6 may be provided in the grid circuit to limit the gridcurrent of tubes lo andle.

The anode of the tube la is coupled with the anodes of the tubes 10 andle by the intermediary of the auxiliary transformers too and we.Resistances me, me and mm are provided to limit the anode currents. Theanodes are fed. by a positive voltage ea. Finally, in the three anodecircuits, the transformers or the resistances are shunted by CondensersC7, C8, C9, C10, C11, C12 and 013. These parts, which did not exist inthe system described in the first example, constitute, as stated above,the device which allows of the alternating lighting and extinguishing ofthe tubes Z0 or Ze, which retransmit the signals. It is indeed known,that once lighted, a gas-filled tube with continuous voltage, from theanode voltage source va, cannot be ex:- tinguished whatever may be thevariations of the grid voltage.

This device of Figure 2 operates in the following manner: Let us supposethat a signal must be retransmitted in the direction 0-2 and that thefirst alternation of the signal has lighted the tube In by the inductionof a positive voltage in the grid circuit. Simultaneously, as aconsequence of the direction in which the winding Co is wound, anegative voltage was induced in the grid of la which therefore could notlight up.

With the next half-cycle of the incoming signal, the voltages induced inthe grids of tubes lo and le take on inverse polarities. Thereupon, thetube la lights up. On its lighting up, by reason of the negligibleinternal resistance of the gas-filled tubes and of the presence of thecapacities C7, C8 and C13, through which the anode circuit may close, apoint of excess anode current is produced. This excess current in theanode circuit of tube la at that instant induces in the anodev circuitof the anode of tube Z0, through the intermediary of mo, a voltageopposed to and higher than 0a. This tube becomes extinguished and, asits grid voltage is at this instant more negative than og, it remainsextinguished as long as the second half-cycle of the signal alternatingcurrent lasts.

At the next half-cycle, tube Zo lights up again and extinguishes tube laby the same phenomenon of excess anode current in the anode circuit oftube Zo which induces a current in the anode circuit of tube la throughtransformer trio and the condensers C9 and C11. And so on for as long asthe alternating signal lasts which applied to terminals 01, O2

Otherwise, the retransmission of the signals and the blocking of thereverse line take place as in the preceding example.

Figure 3 represents a variation of the preceding example as far asconcerns the device for the cyclic extinction of the tubes lo or Ze. Thecyclic extinction of the tubes at the signaling frequency is ensured bythe coupling of the anodes of le and lo by the capacity C15, and of theanodes of la and le by the capacity C14, instead of the inductivecoupling by the transformers tao and tae of Fig. 2. Accordingly, onlythe tubes and the coupling of the anodes are shown, the rest of the planbeing the same as in the preceding example.

The extinguishing is made by the following operation: Assume that asignal is being applied to the terminals 01 Oz and that tube Z0 lightedup; its anode potential is equal to the voltage drop in the tube lo,therefore small before the voltage of va. On the contrary, the tube labeing extinguished, its anode potential is equal to 2m. Condenser C15 istherefore charged. If tube la lights up, the voltage becomes zero acrossthe terminals of condenser 015, which discharges itself into the twotubes Z0 and la in series, confirming the lighting of la andextinguishing 10, for; the discharge current circulates in an inversedirection in this tube Z0 and cuts off the lighting current in the anodecircuit of tube Z0. And so on for the successive alternations of thesignal at the signaling frequency.

All the examples described make use of gasfilled tubes with threeelectrodes, but it is clear that one may, without overstepping thelimits of the invention, utilise tubes allowing of a greater number ofelectrodes. These tubes may have either. a cold cathode or a heatedcathode. The heating circuits have not been shown in the plans.

The arrangements according to the invention apply to the retransmissionof signals constituted by trains of low frequency waves. Those which arefed under continuous anode voltage may transmit signals of severalfrequencies, which allows of increasingtheir practical possibilities forutilisation.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed I declare thatwhat I claim is:

1. In a device for retransmitting signals, two paths connected inparallel between two sections of a two wire telephone line, and eachadapted to transmit the signals in one direction, on each channel arectifier bridge and an input transformer whose primary is connected tothe end of one of the sections of the line and whose secondary isconnected, through the intermediary of said rectifier bridge, to theterminals of a resist ance inserted in the grid circuit of a thyratron,a source of direct voltage negatively biasing the said grid circuit insuch manner as to prevent the ignition of the thyratron in the absenceof received signal received on the input transformer, and, in the anodecircuit of the said thyratron, a source of alternating current of lowfrequency in series with the primary of an output transformer whosesecondary is connected to the end of the other section of the line; theanode circuit of the thyratron of each of the said channels comprisingfurther the primary or a transformer whose secondary is connected,through the intermediary of a bridge of rectifiers to the terminals of aresistance inserted in the grid circuit of the thyratron of the other,so as to prevent the ignition of the latter thyratron when the first isignited.

2. A device for retransmitting signals inserted between two sections ofa two wire telephone line, comprising on the one hand, for the one ofthe directions of transmission an input transformer whose primary isconnected to the end of one of the sections of the line and whosesecondary is inserted in series in the grid circuit of a thyratron, asource of direct voltage negatively biasing the said grid circuit insuch manner as to prevent the ignition of the thyratron in the absenceof signal received on the input transformer, and, in the anode circuitof said thyratron a source of direct voltage in series with the primaryof an output transformer whose secondary is connected to the end of theother section of the line, and on the other hand a second path identicalwith the first, symmetrically arranged for the other direction oftransmission, the anode circuit of the thyratron of each of said pathscomprising further the primary of a transformer whose secondary isconnected, through the intermediary of a rectifier bridge, to theterminals of a resistance inserted in the grid circuit of the thyratronof the other path, in such manner as to prevent the ignition of thislast thyratron when the first is ignited, the retransmitting devicecomprising further a third thyratron in the grid circuit of which areconnected two windings coupled respectively to the primary Winding ofthe input transformer of each of the two paths, the direction of thesewindings being such that when a positive signal is applied to the inputtransformer, a negative signal is applied to the grid of the thirdthyratron and inversely, the anode circuit of. the said third thyratroncomprising a coupling with the anode circuits of the two otherthyratrons, in such manner, that when the said third thyratron isignited, it induces in the said anode circuits a negative voltage whichin abso- '6 lute value exceeds the positive voltage of the sources ofcontinuous current connected to the said anode circuits. a

3. A device according to claim 2, comprising two transformers whoseprimary windings are connected in series in the anode circuit of theauxiliary thyratron, and the secondary windings are connectedrespectively in the anode circuits of the two other thyratrons.

4. A device according to claim 2, comprising two condensers connectedrespectively between the anode of the auxiliary thyratron and the anodeof each of the other two thyratrons.

5. In a two-way device for retransmitting signals, a first pair of lineterminals, a second pair of line terminals, a first gas filled triode, asecond gas filled triode, a source of negative direct current biasvoltage connected for biasing the grid of each of said triodes, meansfor deriving from the signal incident on said first pair of line ter-.minals a derived voltage and applying the same to the grid of said firsttriode in series with the source of negative grid bias therefor, asource of anode potential for each said triode, first translating meanscomprising a transformer for deriving a portion of the output of theanode circuit of said first triode and delivering the same to saidsecond pair of line terminals, first blocking means comprising atransformer and a rectifier for deriving a portion of the output of theanode circuit of said first triode and rectifying the same and applyingthe so rectified derived voltage to the grid of said second triode withnegative blocking polarity in series with the source of negative biasvoltage therefor, means for deriving from the signal. incident on saidsecond pair of line terminals a derived voltage and applying the same tothe grid of said second triode in series with the source of negativegrid bias therefor, second translating means comprising a transformerfor deriving a portion of the output of the anode circuit of said secondtriode and delivering the same to said first pair of line terminals, andsecond blocking means comprising a transformer and a rectifier forderiving a portion of the output of the anode circuit of said secondtriode and rectifying the same and applying the so rectified derivedvoltage to the grid of said first triode with negative blocking polarityin series with the source of negative bias voltage therefor.

6. In a two-way device for retransmitting low frequency signals, a firstpair of line terminals, a second pair of line terminals, a first gasfilled triode, a second gas filled triode, a source of negative directcurrent bias voltage connected for biasing the grid of each of saidtriodes, means for deriving from the signal incident on said first pairof line terminals a derived voltage and applying the same to the grid ofsaid first triode in series with the source of negative grid bias therefor, an anode circuit for said first triode, a direct current source ofanode potential for each said triode connected in its said anodecircuit, an auxiliary source of anode potential for each said triodeperiodically producing positive cyclic pulses of current at thefrequency of the incoming low frequency signal and being connected inits said anode circuit in series with the said direct current sourcethereof, first translating means comprising a transformer for deriving aportion of the output of the anode circuit of said first triode anddelivering the same to said second pair of line terminals, firstblocking means comprising a transformer and a rectifier for deriving aportion of the output of the anode circuit of said firsttriode andrectifying the same andapplying the so rectified derived voltage to thegrid of said second triode with negative blocking polarity in serieswith the source of negative bias voltage therefor, means for derivingfrom the signal incident on said second pair of line terminals a derivedvoltage and applying the same to the grid of said second triode inseries with the source of negative grid bias therefor, secondtranslating mean comprising a transformer for deriving a portion of theoutput of the anode circuit of said second triode and delivering thesame to said first pair of line terminals, and second blocking meanscomprising a transformer and a rectifier for deriving a portion of theoutput of the anode circuit of said second triode and rectifying thesame and applying the so rectified derived voltage to the grid of saidfirst triode with negative blocking polarity in series with the sourceof negative bias voltage therefor.

7. A device according to claim 6, said auxiliary source for each saidtriode being a source of alternating current of the frequency of theincoming signal.

8. A device according to claim 6, and a third gas filled triode, a gridcircuit therefor'comprising a source of negative direct current biasvoltage, an anode circuit therefor comprising a source of anodepotential, means for deriving from the signal incident on each said pairof line terminals a derived voltage and applying the same to the grid ofsaid third triode in series with the source of negative direct currentbias therefor, and said auxiliary source of each of said first andsecond triodes comprising complementary means for deriving energy fromthe anode circuit of said third triode and applying the same to theanode circuit of said first and second triodes respectively.

9. A device according to claim 8, said complementary means being a pairof transformers connected to couple the anode circuit of said thirdtriode to the anode circuit of said first and second triodesrespectively.

10. A device according to claim 8, said complementary means being a pairof condensers connected between the anode of said third triode and theanodes of said first and second triodes respectively and arranged tocouple the anode circuit of said third triode to the anode circuit ofsaid first and second triodes respectively.

11. A device according to claim 6, each said means for deriving from thesignal incident on said first and second pair of line terminals aderived voltage and applying the same to the grid ofsaid first andsecond triodes comprising an auxiliary bridge rectifier and an outputresistance for said auxiliary rectifier in series in the rid circuit ofsaid first and second triodes respectively.

HENRI GARDERE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,510,676 Johnson Oct. '7, 19241,665,698 Gorton Apr. 10, 1928 2,016,261 Wise et al. Oct. 1, 19352,124,848 Powell July 26, 1938

